I’m looking at adding external IP discovery eventually.
Still not clear tbh, what if I need to have 1000 IPs with my EC2 instance with KumoMTA, is that even possible? 
Looks like this is exactly what I have now, but private IPs are limited per network interface
I’m going to be honest and say if you need 1,000 IPs and are asking these kinds of questions you will probably have a bad time.
Sorry Mike, I spent half day on googling and some search on AWS knowledge bases etc, but still not clear lol Looks like this is something very rare